The fin selection of the stainless steel steam heat exchanger.
The steam heat exchanger is the most important auxiliary equipment for drying equipment.
Drying technology involving chemical, pharmaceutical, light industry, food processing, lumber, minerals, and other industries, drying equipment processing various materials and air heat exchanger to meet the requirements of all kinds of dry material of hot air.
Drying is a very energy-intensive operation and the most basic method of reduce the energy consumption is to choose a set of efficient heat transfer device, how to choose the economic air heat exchanger has the vital significance.
The steam heat exchanger is an indirect heat transfer device, consisting of multiple cooling pipes.When steam is used to make a hot medium, the inside of the tube passes through the steam. Due to the different forms of finned material and fin, many specifications have been serialized.
Electric heater has the characteristics of simple structure, high mechanical strength, high thermal efficiency, safe and reliable, easy to install and easy to realize temperature control automation.
The spacing and height of the fin tube steam heat exchanger mainly affect the wing ratio, and the wing ratio has a great relationship with the film heat transfer coefficient of the inner and outer media.
If the coefficient of heat transfer between the inner and outer membrane of the tube is very different, it should choose the finned tube with larger wing ratio, such as steam heating air.
When there is a phase change in the side medium, the difference of heat transfer coefficient is larger, such as the exchange of cold and hot air. When the hot air drops below the dew point, the finned tube steam heat exchanger can be used.
In the absence of phase change in the heat exchange between air and air, or the heat exchange between water and water, it is usually appropriate to use a bare tube.
Of course, the low-fin tube can also be used, because it belongs to the weak heat coefficient, and it is effective to strengthen any side of it.
However, it is not obvious that the excessive wing ratio is not obvious, and the best internal and external contact area is also strengthened, which can be used with threaded or grooved tubes.
The fins of the steam heat exchanger fin are mainly considered to be ash, dust, easy cleaning and other factors, and should be strictly in line with the requirements of equipment on pressure drop.
When arranging, the distance between tube and tube is not easy to be too large. Generally, > 1mm is suitable for cloth tube.In the process of heat transfer, the air is mainly involved in the heat transfer between the fins and the two sides of the fin tube steam heat exchanger.
There is only a small amount of radiative heat transfer in the middle part of the two fin tubes, and the heat transfer effect is not obvious.Because of the wingless film, there is no resistance and the air penetrates easily.In the process of air heating, the unheated cold air will be neutralized with the heated air passing through the middle of the fin, thus reducing the effect of heat exchange.
Compared with the foreign finned tube steam heat exchanger, the tube spacing is only 0.5mm larger than the outer diameter of the fin, and the importance of tube spacing is seen in the arrangement of finned tube.
The tube arrangement of the fin tube steam heat exchanger should be arranged in a normal triangle.After the first row of hot air, resistance in the second row, have certain springback wind, so the whole finned tube 360 ° the phenomenon of heat transfer is no dead corner.
Therefore, we should avoid the isosceles triangle arrangement, and try not to use square arrangement, unless there are special requirements.
Air side pressure drop is a very important parameter in the design, it has a lot to do and the arrangement of finned tube, fin tube arrangement design calculation of narrow gap flow surface and the windward surface ratio, thus according to calculate the velocity of air quality on wind speed, in to the dynamic viscosity of different air temperature, and the coefficient of friction.
Stainless steel steam heat exchanger with stainless steel material as a whole of finned heat exchanger, the part can be divided into full stainless steel and stainless steel two kinds, due to high cost of stainless steel (almost three times the ordinary steel), so the necessary parts for stainless steel can greatly save the cost, cost-effective compared with stainless steel.
So what are the requirements for the design of the steam heat exchanger during cooling air?
1. According to the cooling requirements of the process medium and the water source of the installation, the economic comparison between air cooling and water cooling is conducted to determine the rationality of the use of stainless steel steam heat exchanger.
2. Determine the type of stainless steel steam heat exchanger according to the final temperature and environmental conditions of the required medium (generally refers to the water cold wind)
3. Preliminary estimation of the required heat transfer area under the operating conditions;Selection of equipment structure models for stainless steel steam heat exchanger (refers to the size of tube, fin type, frame, fan, etc.)
4. According to the process of operating conditions and physical properties, the primary model in the following accounting: the coefficient of heat transfer and pressure drop tube membrane, tube outside heat transfer coefficient and pressure drop, the total heat transfer coefficient and effective mean temperature difference, and then calculate the heat transfer area.
If the primary area is insufficient or large, adjust the model and repeat the calculation until the selected model meets the design requirements, then the fan is calculated.
5. According to the production characteristics of the device, the horizontal and vertical plane layout and control scheme of the steam heat exchanger are comprehensively considered.
6. Consideration of noise, anticoagulation and anti-freeze and other aspects.